Changes in Body Composition, Muscle Strength, and Fat Distribution Following Kidney Transplantation

ABSTRACT Rationale and Objective Low muscle mass relative to fat mass (relative sarcopenia) has been associated with mortality and disability but has not been examined following transplantation. We studied how measures of body composition change after receipt of a kidney allograft. Study Design Prospective longitudinal cohort study. Setting and Participants 60 kidney transplant recipients (ages 20-60 years) at the University of Pennsylvania. Exposure Kidney transplantation. Outcomes DXA measures of fat mass index (FMI) and appendicular lean mass index (ALMI; representing muscle mass), CT measures of muscle density (low density represents increased intramuscular adipose tissue), dynamometer measures of leg muscle strength, and physical activity. ALMI relative to FMI (ALMFMI) is an established index of relative sarcopenia. Analytical Approach Measures expressed as age, sex, and race-specific Z-scores for transplant recipients were compared to 327 healthy controls. Regression models were used to identify correlates of change in outcome Z-scores and compare transplant recipients to controls. Results At transplantation, ALMI, ALMIFMI, muscle strength and muscle density Z-scores were lower vs. controls (all p≤0.001). Transplant recipients received glucocorticoids throughout. The prevalence of obesity increased from 18 to 45%. Although ALMI increased following transplantation (p Limitations Lack of muscle biopsies precluded assessment of muscle histology and metabolism. Conclusions The two-year interval following kidney transplantation was characterized by gains in muscle mass and strength that were outpaced by gains in fat mass resulting in persistent relative sarcopenia.